1. Field of the Invention
The present invention relates to a surveillance monitor system for monitoring fires and thefts, in particular one designed so that it can recognize and warn of both fires and thefts by monitoring images from the same television camera. The invention also relates to a surveillance monitor system which detects a fire by a fire detection method using images of a surveillance area, from which the system deduces the radiant energy of the radiant energy source and, from this data, judges whether there is a fire.
2. Description of the Related Art
There are known fire monitor systems using television cameras and having the virtue of providing a great quantity of information and monitoring a large surveillance area. Also there are known burglary monitor systems using television cameras.
An example of a fire monitor system using a television camera is Japanese Patent Laid Open 1-268570, a fire extinguishing system.
This system can recognize the size of a flame and detect the position of a flame by processing luminance signals of a monitor image obtained by a monitor television camera. In more detail, it compares an image's luminance signals with a threshold value, and judges a part of the image whose luminance signals exceed the threshold value to be a fire source. As an example, this method for detecting a radiant energy source based on luminance signals is used for detecting a radiant energy source for the purpose of controlling an extinguishing system in Japanese Patent Laid Open 1-268572. If there are a plurality of flames it extinguishes the fire by controlling the nozzle based on arranging the targets to be extinguished in order of size from the largest flame downwards.
Again, an example of an anti-burglary monitor system using a television camera is Japanese Patent Laid Open 2-171897, an abnormality monitor system. In this system a reference image of the surveillance area in its normal state is memorized beforehand, and edges in a current image obtained by the television camera are sampled and compared with the reference image. Then only (an edge or) edges which appear/(s) in the current image but not in the reference image are/(is) sampled, and if the number of pixels of the area surrounded by the edge exceeds the threshold value number, it recognizes it as an intruder. Also the new edge information of current images is constantly logically added to amend the reference image so that, even though the shadows of objects in the room move with the movement of the sun, these shadows are not mistakenly recognized as intruders.
However, known monitor systems using television cameras were divided into systems monitoring fires and systems for anti-burglary monitoring, and thought of separately, so that even if they were installed in the same building, they were installed as separate systems and also the data from the two systems was processed separately, resulting in the following problems.
First, compared with monitor systems using presently used fire sensors and intruder detectors the system cost of a monitor system using a television camera was rather high because an image processor exclusively for processing the enormous quantity of data were used. As a result surveillance monitor systems using a television camera are not in widespread use.
Second, the image processing technology for recognizing fires and for recognizing intruders had not been perfected or brought to maturity, and therefore there was still the possibility of some other cause being mistakenly recognized as a fire or intruder. Thus, the automatic issuing of an alarm based on image recognition was a problem from the point of view of reliability, just as it was with conventional fire sensors and intruder detectors.
Third, particularly in the case of fire detection based on the known method depending solely on luminance signals, lights other than fires, for example reflected light of headlights, or sunlight, sometimes caused the luminance signals to exceed the threshold value. As a result it was difficult to distinguish correctly between changes in luminance signals due to a fire and change in luminance signals due to other causes, and thus fire detection systems using images had the disadvantage of not being sufficiently reliable.